A question about typesetting for clarinet music

[Charles]

I have been given an orchestral part for clarinet in A - "Morning Mood" 
from Greig's Peer Gynt Suite.

I have been asked to provide a transposed score for Clarinet in B flat.

So far, I have only typeset piano music with Lilypond.

I wanted to check the procedure I should follow to achieve this task.

First of all, this piece of music has one sharp.  (G major)
Since I am now transposing for a B flat clarinet which sounds one
semitone higher than a Clarinet A when the player plays a note
as written, I should then flatten every note in the supplied score
by a semitone using this statement:
 \transpose  bes a

This is my approach:

1. Typeset the music as supplied in G major

2. Insert the transpose statement

3. What key signature should I publish in? 

4. Publish the score.


Thanks
Charles